Lithology

Lithology

The upper and lower Bakken members are similar in that they are hard, siliceous, pyritic, fissile, brownish black to dark
black, often noncalcareous, and organic-rich shales.3 The shales are
very uniform throughout their extents; however, some cores of the lower shale have thin (3 feet) black limestone that is
coarsely crystalline and significantly lower in organic content.

Middle Member

The middle member’s lithology is highly variable and consists of five distinct lithofacies. The unit is well-sorted
(although bioturbation is common); well-cemented with calcite, dolomite, or silica; and light to medium gray in color.
All lithologies within the middle member have low primary permeability and porosity.